(CNN) -- The number of chemicals known to be toxic to children's developing brains has doubled over the last seven years, researchers said.

Dr. Philip Landrigan at Mount Sinai School of Medicine in New York and Dr. Philippe Grandjean from Harvard School of Public Health in Boston, authors of the review published Friday in The Lancet Neurology journal, say the news is so troubling they are calling for a worldwide overhaul of the regulatory process in order to protect children's brains.

"We know from clinical information on poisoned adult patients that these chemicals can enter the brain through the blood brain barrier and cause neurological symptoms," said Grandjean.

"When this happens in children or during pregnancy, those chemicals are extremely toxic, because we now know that the developing brain is a uniquely vulnerable organ. Also, the effects are permanent."....